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Haematology HK > Haemoglobinopathy > Flashcards

Haemoglobinopathy Flashcards

1
Q

describe the structure of a haemoglobin molecule

A

2 alpha globin chains
2 beta globin chains
one haem group (iron in porphyrin ring) per globin chain

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2
Q

what are the major forms of Hb

A

HbA (2 alpha, 2 beta)
HbA2 (2 alpha, to delta)
HbF (2 alpha, 2 gamma)

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3
Q

what is the most abundant type of haemoglobin in adults

A

HbA

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4
Q

what chromosome are the genes for alpha globins on and how many are there

A

chromosome 16
2 alpha genes per chromosome
4 alpha genes per cell

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5
Q

what chromosome are the genes for beta globins on and how many are there

A

chromosome 11
one beta gene per chromosome
2 genes per cell

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6
Q

when do we express HbF as opposed to HbA

A

HbF - foetal Hb

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7
Q

what are haemoglobinopathies

A

hereditary conditions affecting globin chain synthesis

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8
Q

haemoglobinopathies are generally dominant/recessive disorders

A

autosomal recessive

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9
Q

what is a thalassaemia

A

decreased rate of Hb synthesis (reduced or absent)

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10
Q

what happens in structural haemoglobin variant disorders

A

production of structurally abnormal globin chains

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11
Q

what are the 2 types of thalassaemias

A

alpha chain

beta chain

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12
Q

what type of anaemia do thalassaemias cause

A

microcytic hypochromatic

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13
Q

geographical risk factor for thalassaemia

A

tropical areas with high incidences of malaria

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14
Q

what does the imbalance of globin chain within red cells cause

A

ineffective erythropoiesis and premature red cell death

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15
Q

how many alpha genes are missing in a thal trait

A

one or two

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16
Q

how many alpha genes are missing in HbH disease

A

3

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17
Q

what is the condition where no functioning alpha genes

A

Hb Barts hydrops fetalis

18
Q

how would you differentiate thalassaemia from iron deficiency

A

both would be microcytic anaemia (low Hb, low MCV)

thalassaemia has a normal ferritin level with raised red cell count)

19
Q

clinical features of HbH disease

A

anaemia (possibly transfusion dependant)
splenomegaly
jaundice

20
Q

management of HbH disease

A

splenectomy

potentially transfusion if required

21
Q

clinical features of Hb Barts hydrops fetalis

A 
severe anaemia 
cardiac failure 
growth retardation
hepatosplenomegaly 
die in utero
22
Q

how many faulty beta genes in B thalassaemia trait

A

one

23
Q

how many faulty beta genes in thalassaemia intermedia

A

two genes causing reduced B chain production
OR
one gene causing reduced B chain production and one causing no B chain production

24
Q

how many faulty beta chains in thalassaemia major

A

both genes causing no production of beta chains

25
Q

presentation of thalassaemia major

A 
6-24 months (when HbF falls off)
pallor, failure to thrive
hepatosplenomegaly 
skeletal changes
organ damage
26
Q

management of thalassaemia major

A

transfusion
monitor iron levels - prevent over-absorption
bone marrow transplant if before complications

27
Q

consequences of iron overload

A 
diabetes 
osteoporosis
impaired growth 
cardiac disease 
liver disease
28
Q

management of iron overload

A

iron chelating drugs - desferrioxamine

29
Q

what causes sickle cell anaemia

A

point mutation on B globin gene causing HbS to be formed

30
Q

what happens to HbS if exposed to low O2 sats

A

polymerises - distorts cell membrane

31
Q

how many abnormal genes in sickle cell trait

A

1

32
Q

how many abnormal beta genes in sickle cell anaemia

A

2

33
Q

when may symptoms arise in sickle cell trait

A

severe hypoxia eg high altitude, under anaesthesia

34
Q

what is sickle crisis

A

episodes of tissue infarction due to vascular occlusion

35
Q

where is sickle crisis likely to occur

A

digits, bone marrow, lung, spleen, CNS

36
Q

what are some consequences of sickle cell anaemia

A

chronic haemolysis

hyposplenism (from multiple splenic infarcts)

37
Q

triggers of sickle crisis

A 
hypoxia 
dehydration 
infection 
cold 
stress/disease
38
Q

management of sickle crises

A 
opiate analgesia 
hydration 
rest
O2
antibiotics (in infection)
red cell transfusion if severe (neurological symptoms, chest crisis)
39
Q

long term management of sickle cell anaemia

A

reduce risk of infection - vaccines of encapsulated bacteria(pneumococcus, meningococcus, haemophilus) and prophylactic penicillin
folic acid
hydroxycarbamide (induces HbF production)

40
Q

what are investigations needed to detect haemoglobinopathy

A

FBC, Hb, red cell indices
blood film
high performance liquid chromatography/gel electrophoresis (looks at quantities of different Hb)

41
Q

what investigation is needed to confirm a thalassaemia trait

A

DNA testing

Haematology HK (22 decks)

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